1. Field of the Invention
This invention relates generally to orbital welders, and more particularly to a novel orbital welder facilitating easier tube alignment and capable of forming non-planar welds.
2. Description of the Background Art
Orbital welders are widely used in the construction of fluid handling systems, for example semiconductor processing equipment. Known orbital welders join metal tubes in an end-to-end fashion by forming a flat, circular weld around the circumference of the tube""s open end. One problem encountered by conventional orbital welders is that the ends of the tubes which are to be joined must be carefully aligned prior to performing the welding operation. Additionally, because known orbital welders are limited to forming flat, circular welds (i.e., a circular weld lying in a single plane), special tube preparation is required to weld a cross or a tee (xe2x80x9cTxe2x80x9d) joint.
FIG. 1 is a top plan view of a typical orbital welder 100, which includes an insulating housing 102, tube clamps 104 and 106, a rotor 108, a weld tip 110, and a rotation and voltage controller 112. Clamps 104 and 106 hold tubes 114 and 116, respectively, in position for welding, and are maintained at a common voltage (e.g., ground) and in electrical contact with tubes 114 and 116. Rotor 108 is disposed within housing 102 so as to be rotatable about an axis 118 passing through the center of the open ends of tubes 114 and 116. Housing 102 provides electrical insulation between rotor 108 and clamps 104 and 106. Rotation and voltage controller 112 functions to rotate rotor 108 within housing 102, and to apply a voltage, via rotor 108, to attached weld tip 110.
FIG. 2 shows a cross-sectional view of orbital welder 100. As controller 112 rotates rotor 108 about axis 118 and applies a high voltage to weld tip 110, an arc weld 202 is formed between the open ends of tubes 114 and 116. Because clamps 104 and 106 are held at the common voltage, they must be displaced a safe distance from weld tip 110, so as not to generate an arc therebetween. The distance between clamps 104 and 106 and the open ends of tubes 114 and 116 makes alignment of the open ends of tubes 114 and 116 more difficult. Moreover, the interior chambers of known orbital welders are dark, and, therefore, visual confirmation of proper alignment is difficult.
FIG. 3 is a cross-sectional view of an orbital welder 300 capable of forming a flat xe2x80x9cTxe2x80x9d weld. Orbital welder 300 includes an insulating housing 302, a tube clamp 304, a xe2x80x9cTxe2x80x9d fitting clamp 306, a rotor 308, a weld tip 310, and a rotation and voltage controller 312.
Orbital welder 300 functions similarly to orbital welder 100. Clamps 304 and 306 hold a tube 314 and a T-fitting 316 in position and at a common voltage. Rotation and voltage controller 312 causes rotor 312 to rotate about an axis 318, and applies a high voltage, via rotor 308, to weld tip 310. As rotor 308 rotates about axis 318, a weld 320 is formed between the open ends of tube 314 and T-fitting 316.
FIG. 4 is a perspective view of T-fitting 316. In order to make T-fitting 316 from a standard piece of tube stock 402, an opening 404 is first cut or ground into the tube stock 402. Next, an extrusion process is required to draw the tube material surrounding opening 404 into an extended portion 406 defining a flat circular opening 408. Because the extrusion process is relatively complex, workers cannot weld T-joints quickly and easily on job sites, from standard tube stock. Additionally, for commonly used 0.25 in. O.D. tubing, the extrusion process is generally limited to tubes with a wall thickness of 0.028 in. or less, and is therefore unavailable for the preferred 0.035 in. walled tubing.
What is needed is an orbital welder capable of welding T-joints and cross-joints from standard tube stock. What is also needed is an orbital welder which facilitates easy alignment of the tube pieces which are to be welded. What is also needed is an orbital welder with that facilitates easy visual confirmation of proper alignment.
A novel orbital welder capable of forming non-planar orbital welds is described. The use of non-planar orbital welds facilitates the construction of various tube joints, including T-joints, cross-joints, and end-to-end joints, form standard tube stock by workers in the field.
One embodiment includes a weld tip, a rotational controller, and a translational controller. The rotational controller causes the weld tip to rotate about an axis passing through the tube to be welded. As the weld tip rotates about the axis, the translational controller causes the weld tip to move longitudinally with respect to the axis. Thus, non-planar orbital welds can be formed.
In a particular embodiment, the translational controller includes a rotor which is slidably disposed in an insulating body, and the weld tip is fixed directly to the rotor. As the rotor rotates about the axis, the translational controller causes the rotor to move longitudinally with respect to the axis of rotation, such that the weld tip follows a non-planar weld pattern.
In another particular embodiment, the rotational controller includes a rotor disposed to rotate about the axis, but remains within the plane of rotation. The translational controller includes a carrier that is slidably attached to the rotor, and the weld tip is fixed to the carrier. As the rotor rotates about the axis, the carrier moves longitudinally with respect to the axis, such that the weld tip follows a non-planar weld pattern. In a more particular embodiment, a portion of the carrier is biased against a surface of a cam block, and optionally includes a wheel for reducing the friction between the carrier and the cam block. The surface of the cam block is contoured to displace the carrier longitudinally with respect to the axis of rotation as the rotor rotates about the axis. Alternatively, the surface of the cam block is flat, and the cam block is displaced longitudinally as the rotor rotates about the axis of rotation.
In an alternate embodiment, the translational controller includes a wall with a groove that defines the desired weld pattern. A guide pin extends from the carrier into the groove. As the rotor rotates about the axis of rotation, the pin follows the groove, moving the carrier longitudinally with respect to the axis of rotation.
Another embodiment, particularly suited for welding cross-joints includes two weld tips, two rotational controllers, and two translational controllers. In a particular embodiment, each translational controller includes a rotor which rotates about an axis of rotation, and which moves longitudinally with respect to the axis. Each weld tip is fixed to one of the rotors, and, therefore, moves along a non-planar circular path. In an alternate embodiment, each translational controller includes a rotor which rotates about an axis, but which is fixed in the plane of rotation. Each weld tip is fixed to a separate carrier which is slidably attached to a respective one of the rotors. Each of the carriers is biased against an associated one of two cam blocks. As the rotors rotate about the axes of rotation, the cam blocks displace the carriers longitudinally. The attached weld tips follow non-planar orbital weld patterns. Optionally, a single rotational controller controls both rotors
Any of the described embodiments may include an optional light source for illuminating the interior chamber of the orbital welder. In one embodiment, the body of the orbital welder includes a light conducting portion for transmitting light from the light source to the interior chamber. In a more particular embodiment, the light conducting portion is formed as a layer of the body of the orbital welder, and the light source is disposed in an opening in, or along the edge of, the light conducting layer. Optionally, the light source is disposed within the interior chamber of the welder. Types of light sources used may include, but are not limited to, light-emitting diodes, incandescent bulbs, and optical fibers transmitting light from a remote source. A switch, disposed on the exterior surface of the body or in an external controller, controls the operation of the light source.